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Cold waves have gripped several parts of northwest India from December 15, 2022 that are expected to continue for the next few days as well. However, the season could still end up warmer than normal and impact the Rabi crop season, especially for fruit farmers in hilly states.
The cold waves were anomalous as there was no mention of them in the India Meteorological Department’s (IMD) seasonal forecast for the winter season, issued December 1, 2022.
IMD had predicted a warmer-than-normal winter season from December 2022 to February 2023 in the northwest, northeast and some central states of the country.
The cold waves started in Punjab on December 15. The next day, they spread to northern parts of Rajasthan and Himachal Pradesh and Haryana December 18.
But all these states did not bear with cold waves on all days between December 15 and December 19. Punjab experienced cold waves on five days, Rajasthan on three days, Himachal Pradesh on two days and Haryana saw only one cold day.
IMD cited dry north/north westerly winds blowing down from the Himalayas as the reason for the cold waves.
These winds are typical for this time of the year, said Akshay Deoras, research scientist at the National Centre for Atmospheric Science and Department of Meteorology, University of Reading, the United Kingdom.
“Strong western disturbances striking India usually disrupt this wind pattern for a few days, causing the minimum temperatures to rise,” he said. “IMD did not mention cold waves in the seasonal forecast because it is impossible to predict them on the seasonal time scale.”
“Cold spells could be predicted on the sub-seasonal time scale (looking about two weeks to one month ahead). Even in the absence of western disturbances, cold spells can occur. Still, the maximum temperatures in such a situation remain high in the absence of cloud cover,” Deoras told Down To Earth.
“Western disturbances are episodic events and weather is an everyday phenomenon. So the two are not contradictory since the entire season may end up being warmer than normal,” Raghu Murtugudde, a climate scientist at the University of Maryland and Indian Institute of Technology, Bombay, told DTE.
“But winter will have cold bursts. I think a large lazy low-pressure system in the Bay of Bengal is pulling in the winds from the northeast and also affecting the westerly-northwesterly flow into northwest India. I would say it’s just weather,” he added.
The low-pressure area formed in the southeast Bay of Bengal on December 15 and has moved exceedingly slowly over the past week. It has not intensified further into a depression.
In its December 20 press release, IMD still predicted that the system would move slowly towards the Sri Lanka coast over the subsequent two days.
The current dry conditions over northwestern states will continue till December 24. After that, a weak western disturbance may bring some respite on December 25 and 26.
Light precipitation is expected December 25-26 due to a weak western disturbance. However, the dry spell is expected to continue in plains, with increasing chances of 2022 ending on a dry note.
The main concern right now is warm conditions, according to Deoras. “Good rainfall in October has boosted the sowing of Rabi crops and irrigation could be applied where available. However, fruit growers in hilly states are particularly worried about adverse impacts on the yield,” he added.
In particular, Uttarakhand and Himachal Pradesh have witnessed a very warm December so far, with at least 3 degrees Celsius above average maximum temperature, Deoras further said.